Stent delivery under direct visualization

ABSTRACT

Stent delivery under direct visualization utilizing an imaging hood is described herein. A stent may be delivered and placed in or around lesions, e.g., ostial lesions, through a delivery catheter while being directly visualized via an imaging hood. A pre-delivery assessment probe may also be advanced to the desired site for accurate placement of the stent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Prov. Pat. App. 61/026,795 filed Feb. 7, 2008, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to stent delivery systems which may be used to place one or more stents along a lesion. More particularly, the present invention relates to methods and apparatus for the delivery of one or more stents along a lesion, such as an ostial lesion or along a stenosed region (e.g., caused by atherosclerotic plaque) at various locations, for instance along the coronary vessels, renal arteries, etc., while directly visualizing the tissue region.

BACKGROUND OF THE INVENTION

Conventional devices for visualizing interior regions of a body lumen are known. For example, ultrasound devices have been used to produce images from within a body in vivo. Ultrasound has been used both with and without contrast agents, which typically enhance ultrasound-derived images.

Other conventional methods have utilized catheters or probes having position sensors deployed within the body lumen, such as the interior of a cardiac chamber. These types of positional sensors are typically used to determine the movement of a cardiac tissue surface or the electrical activity within the cardiac tissue. When a sufficient number of points have been sampled by the sensors, a “map” of the cardiac tissue may be generated.

Another conventional device utilizes an inflatable balloon which is typically introduced intravascularly in a deflated state and then inflated against the tissue region to be examined. Imaging is typically accomplished by an optical fiber or other apparatus such as electronic chips for viewing the tissue through the membrane(s) of the inflated balloon. Moreover, the balloon must generally be inflated for imaging. Other conventional balloons utilize a cavity or depression formed at a distal end of the inflated balloon. This cavity or depression is pressed against the tissue to be examined and is flushed with a clear fluid to provide a clear pathway through the blood.

However, such imaging balloons have many inherent disadvantages. For instance, such balloons generally require that the balloon be inflated to a relatively large size which may undesirably displace surrounding tissue and interfere with fine positioning of the imaging system against the tissue. Moreover, the working area created by such inflatable balloons are generally cramped and limited in size. Furthermore, inflated balloons may be susceptible to pressure changes in the surrounding fluid. For example, if the environment surrounding the inflated balloon undergoes pressure changes, e.g., during systolic and diastolic pressure cycles in a beating heart, the constant pressure change may affect the inflated balloon volume and its positioning to produce unsteady or undesirable conditions for optimal tissue imaging. Additionally, imaging balloons are subject to producing poor or blurred tissue images if the balloon is not firmly pressed against the tissue surface because of intervening blood between the balloon and tissue.

Accordingly, these types of imaging modalities are generally unable to provide desirable images useful for sufficient diagnosis and therapy of the endoluminal structure, due in part to factors such as dynamic forces generated by the natural movement of the heart. Moreover, anatomic structures within the body can occlude or obstruct the image acquisition process. Also, the presence and movement of opaque bodily fluids such as blood generally make in vivo imaging of tissue regions within the heart difficult.

Other external imaging modalities are also conventionally utilized. For example, computed tomography (CT) and magnetic resonance imaging (MRI) are typical modalities which are widely used to obtain images of body lumens such as the interior chambers of the heart. However, such imaging modalities fail to provide real-time imaging for intra-operative therapeutic procedures. Fluoroscopic imaging, for instance, is widely used to identify anatomic landmarks within the heart and other regions of the body. However, fluoroscopy fails to provide an accurate image of the tissue quality or surface and also fails to provide for instrumentation for performing tissue manipulation or other therapeutic procedures upon the visualized tissue regions. In addition, fluoroscopy provides a shadow of the intervening tissue onto a plate or sensor when it may be desirable to view the intraluminal surface of the tissue to diagnose pathologies or to perform some form of therapy on it.

In one particular treatment, intravascular stents are commonly used to maintain the patency of a vascular lumen. Conventional stent delivery systems typically employ intravascular ultrasound (IVUS) for selecting the appropriate stent and placing it at the site of lesions, e.g., ostial lesions. However, such assessment and placement methods are not accurate. For instance, the treatment site may be located in the right coronary artery immediately adjacent to the ostium in the aortic wall. In such instances, it is often difficult to accurately position an intravascular stent such that the stent does not extend too far proximal to the ostium. Accuracy in placing the stent at the desired location is typically affected by, e.g., limited visualization of the ostium, angulations of the aorto-coronary segment, and the difficulties in the placement of the guiding catheter.

Accurate positioning of the stent along the ostial lesion is particularly desirable because (a) if the stent is placed too proximal to the ostium, the protrusion of the stent into the aortic lumen can cause thrombus or other complications; and (b) if the stent is placed too distal to the ostium, the stent may not be able to subdue the ostial lesion completely thereby resulting in low success rate and high incidence of re-stenosis or recurrence of arterial blockage.

Thus, methods and/or apparatus which are able to allow for accurate positioning of the stent relative to the ostial lesion is highly desirable.

SUMMARY OF THE INVENTION

A tissue imaging and manipulation apparatus that may be utilized for procedures within a body lumen, such as the heart, in which visualization of the surrounding tissue is made difficult, if not impossible, by medium contained within the lumen such as blood, is described below. Generally, such a tissue imaging and manipulation apparatus comprises an optional delivery catheter or sheath through which a deployment catheter and imaging hood may be advanced for placement against or adjacent to the tissue to be imaged.

The deployment catheter may define a fluid delivery lumen therethrough as well as an imaging lumen within which an optical imaging fiber or assembly may be disposed for imaging tissue. When deployed, the imaging hood may be expanded into any number of shapes, e.g., cylindrical, conical as shown, semi-spherical, etc., provided that an open area or field is defined by the imaging hood. The open area is the area within which the tissue region of interest may be imaged. The imaging hood may also define an atraumatic contact lip or edge for placement or abutment against the tissue region of interest. Moreover, the distal end of the deployment catheter or separate manipulatable catheters may be articulated through various controlling mechanisms such as push-pull wires manually or via computer control

The deployment catheter may also be stabilized relative to the tissue surface through various methods. For instance, inflatable stabilizing balloons positioned along a length of the catheter may be utilized, or tissue engagement anchors may be passed through or along the deployment catheter for temporary engagement of the underlying tissue.

In operation, after the imaging hood has been deployed, fluid may be pumped at a positive pressure through the fluid delivery lumen until the fluid fills the open area completely and displaces any blood from within the open area. The fluid may comprise any biocompatible fluid, e.g., saline, water, plasma, Fluorinert™, etc., which is sufficiently transparent to allow for relatively undistorted visualization through the fluid. The fluid may be pumped continuously or intermittently to allow for image capture by an optional processor which may be in communication with the assembly.

In an exemplary variation for imaging tissue surfaces within a heart chamber containing blood, the tissue imaging and treatment system may generally comprise a catheter body having a lumen defined therethrough, a visualization element disposed adjacent the catheter body, the visualization element having a field of view, a transparent fluid source in fluid communication with the lumen, and a barrier or membrane extendable from the catheter body to localize, between the visualization element and the field of view, displacement of blood by transparent fluid that flows from the lumen, and an instrument translatable through the displaced blood for performing any number of treatments upon the tissue surface within the field of view. The imaging hood may be formed into any number of configurations and the imaging assembly may also be utilized with any number of therapeutic tools which may be deployed through the deployment catheter.

More particularly in certain variations, the tissue visualization system may comprise components including the imaging hood, where the hood may further include a membrane having a main aperture and additional optional openings disposed over the distal end of the hood. An introducer sheath or the deployment catheter upon which the imaging hood is disposed may further comprise a steerable segment made of multiple adjacent links which are pivotably connected to one another and which may be articulated within a single plane or multiple planes. The deployment catheter itself may be comprised of a multiple lumen extrusion, such as a four-lumen catheter extrusion, which is reinforced with braided stainless steel fibers to provide structural support. The proximal end of the catheter may be coupled to a handle for manipulation and articulation of the system.

To provide visualization, an imaging element such as a fiberscope or electronic imager such as a solid state camera, e.g., CCD or CMOS, may be mounted, e.g., on a shape memory wire, and positioned within or along the hood interior. A fluid reservoir and/or pump (e.g., syringe, pressurized intravenous bag, etc.) may be fluidly coupled to the proximal end of the catheter to hold the translucent fluid such as saline or contrast medium as well as for providing the pressure to inject the fluid into the imaging hood.

In treating tissue regions which are directly visualized, as described above, one particular treatment involves deploying a stent within a vessel lumen or ostium while under direct visualization. An introducer sheath may be introduced into the patient's body utilizing conventional approaches such that the sheath is advanced intravascularly through the aorta where a guidewire may be advanced through the sheath and into, e.g., the right coronary artery. The treatment may be affected not only within and around the right coronary artery, but also the left coronary artery, left anterior descending artery, left circumflex artery, or any other vessel accessible by the assembly. As the guidewire is positioned within, e.g., the vessel lumen, the deployment catheter and hood may be deployed from the sheath and advanced along the guidewire until the circumference of the hood contacts against or in proximity to the ostium. Once the hood is in contact against the ostium, the clearing fluid may be introduced within the open area of the hood to purge the blood from the hood interior to provide a clear field through which an imaging element positioned within or along the hood may visualize through to view the underlying tissue surrounding the ostium and at least a portion of the vessel wall extending into the lumen.

A stent delivery assembly having an inflatable balloon in an un-inflated low-profile configuration and a stent crimped or otherwise positioned upon the balloon may be advanced through the catheter and distally out from the hood until the stent assembly is positioned in proximity or adjacent to, e.g., an ostial lesion, which is to be treated. The imaging element may be used to directly visualize at least partially into the lumen as the purged clearing fluid exits the hood and down through the lumen to provide an image of the lesion to be treated.

With the stent assembly desirably positioned and confirmed by direct visualization, the balloon may be inflated to expand the stent over the lesion, also while under visualization. In other variations, the balloon carrying the stent may be integrated with a visualization balloon positioned proximally of the stent assembly rather than a hood. The balloon may be subsequently deflated and then retracted back into the hood and the catheter leaving the deployed stent positioned desirably within the lumen. The imager may be used to visually confirm the deployment and positioning of the stent within the lumen.

In determining the size of the ostial lesion to be treated, the imaging capabilities of the hood may be utilized for optimally treating the patient by directly measuring not only the lesion but also the diameter of the vessel lumen for determining an appropriate stent to be deployed as the diameter of the vessel as well as the axial length of the lesion may affect the shape and size of the stent.

One example utilizes a measurement catheter having a number of gradations with known distances which may be advanced through the hood and into the lumen. With the purging fluid introduced through the hood and into the lumen, the markings on the catheter may be viewed and compared to the lesion directly to provide a more accurate measurement of the lesion length than provided by a fluoroscopic image alone. In other variations, expandable baskets or members each having a known expanded diameter may be positioned along a support catheter and advanced distally from the hood and into the lumen to measure a diameter of the vessel interior. The inner diameter of the vessel can thus be calculated by considering the diameter of the member which is blocked from entering the ostium. With the calculated length and diameter of the vessel and lesion to be treated, an appropriate stent may be selected for placement at the ostial lesion.

In yet another variation, a deployment catheter may utilize a hood having an angled interface which is angled relative to the catheter. The asymmetric slanted hood may be used to facilitate navigation within the aorta as the hood may be better able to engage against a tissue region or ostium and establish visualization without the need to steer and/or articulate the catheter shaft perpendicularly within the narrow aorta lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a side view of one variation of a tissue imaging apparatus during deployment from a sheath or delivery catheter.

FIG. 1B shows the deployed tissue imaging apparatus of FIG. 1A having an optionally expandable hood or sheath attached to an imaging and/or diagnostic catheter.

FIG. 1C shows an end view of a deployed imaging apparatus.

FIGS. 2A and 2B show one example of a deployed tissue imager positioned against or adjacent to the tissue to be imaged and a flow of fluid, such as saline, displacing blood from within the expandable hood.

FIGS. 3A and 3B show examples of various visualization imagers which may be utilized within or along the imaging hood.

FIGS. 4A and 4B show perspective and end views, respectively, of an imaging hood having at least one layer of a transparent elastomeric membrane over the distal opening of the hood.

FIGS. 5A and 5B show perspective and end views, respectively, of an imaging hood which includes a membrane with an aperture defined therethrough and a plurality of additional openings defined over the membrane surrounding the aperture.

FIG. 6 illustrates an example of a system configured for visualization and stent delivery.

FIGS. 7A to 7C show partial cross-sectional views of deploying a stent intravascularly within a coronary artery while under direct visualization.

FIGS. 8A to 8C show partial cross-sectional detail views of a stent assembly introduced and deployed within a vessel while under direct visualization.

FIG. 9A shows a partial cross-sectional view of a measurement catheter deployed within a vessel for directly measuring a length of a lesion.

FIG. 9B shows a partial cross-sectional view of one or more measurement baskets or expandable members which may be utilized to measure an inner diameter of the vessel.

FIGS. 10A to 10C illustrate side views of measurement baskets or expandable members which may be deployed sequentially in determining the inner diameter of a vessel.

FIGS. 11A to 11E illustrate another variation where a stent may be positioned upon a balloon integrated with a visualization balloon positioned proximally of the stent for deployment within a vessel.

FIGS. 12A and 12B show a side view of a hood variation which utilizes an angled interface and the angled hood deployed within the body against an ostium.

DETAILED DESCRIPTION OF THE INVENTION

A tissue-imaging and manipulation apparatus described herein is able to provide real-time images in vivo of tissue regions within a body lumen such as a heart, which is filled with blood flowing dynamically therethrough and is also able to provide intravascular tools and instruments for performing various procedures upon the imaged tissue regions. Such an apparatus may be utilized for many procedures, e.g., facilitating transseptal access to the left atrium, cannulating the coronary sinus, diagnosis of valve regurgitation/stenosis, valvuloplasty, atrial appendage closure, arrhythmogenic focus ablation, among other procedures.

One variation of a tissue access and imaging apparatus is shown in the detail perspective views of FIGS. 1A to 1C. As shown in FIG. 1A, tissue imaging and manipulation assembly 10 may be delivered intravascularly through the patient's body in a low-profile configuration via a delivery catheter or sheath 14. In the case of treating tissue, it is generally desirable to enter or access the left atrium while minimizing trauma to the patient. To non-operatively effect such access, one conventional approach involves puncturing the intra-atrial septum from the right atrial chamber to the left atrial chamber in a procedure commonly called a transseptal procedure or septostomy. For procedures such as percutaneous valve repair and replacement, transseptal access to the left atrial chamber of the heart may allow for larger devices to be introduced into the venous system than can generally be introduced percutaneously into the arterial system.

When the imaging and manipulation assembly 10 is ready to be utilized for imaging tissue, imaging hood 12 may be advanced relative to catheter 14 and deployed from a distal opening of catheter 14, as shown by the arrow. Upon deployment, imaging hood 12 may be unconstrained to expand or open into a deployed imaging configuration, as shown in FIG. 1B. Imaging hood 12 may be fabricated from a variety of pliable or conformable biocompatible material including but not limited to, e.g., polymeric, plastic, or woven materials. One example of a woven material is Kevlar® (E. I. du Pont de Nemours, Wilmington, Del.), which is an aramid and which can be made into thin, e.g., less than 0.001 in., materials which maintain enough integrity for such applications described herein. Moreover, the imaging hood 12 may be fabricated from a translucent or opaque material and in a variety of different colors to optimize or attenuate any reflected lighting from surrounding fluids or structures, i.e., anatomical or mechanical structures or instruments. In either case, imaging hood 12 may be fabricated into a uniform structure or a scaffold-supported structure, in which case a scaffold made of a shape memory alloy, such as Nitinol, or a spring steel, or plastic, etc., may be fabricated and covered with the polymeric, plastic, or woven material. Hence, imaging hood 12 may comprise any of a wide variety of barriers or membrane structures, as may generally be used to localize displacement of blood or the like from a selected volume of a body lumen or heart chamber. In exemplary embodiments, a volume within an inner surface 13 of imaging hood 12 will be significantly less than a volume of the hood 12 between inner surface 13 and outer surface 11.

Imaging hood 12 may be attached at interface 24 to a deployment catheter 16 which may be translated independently of deployment catheter or sheath 14. Attachment of interface 24 may be accomplished through any number of conventional methods. Deployment catheter 16 may define a fluid delivery lumen 18 as well as an imaging lumen 20 within which an optical imaging fiber or assembly may be disposed for imaging tissue. When deployed, imaging hood 12 may expand into any number of shapes, e.g., cylindrical, conical as shown, semi-spherical, etc., provided that an open area or field 26 is defined by imaging hood 12. The open area 26 is the area within which the tissue region of interest may be imaged. Imaging hood 12 may also define an atraumatic contact lip or edge 22 for placement or abutment against the tissue region of interest. Moreover, the diameter of imaging hood 12 at its maximum fully deployed diameter, e.g., at contact lip or edge 22, is typically greater relative to a diameter of the deployment catheter 16 (although a diameter of contact lip or edge 22 may be made to have a smaller or equal diameter of deployment catheter 16). For instance, the contact edge diameter may range anywhere from 1 to 5 times (or even greater, as practicable) a diameter of deployment catheter 16. FIG. 1C shows an end view of the imaging hood 12 in its deployed configuration. Also shown are the contact lip or edge 22 and fluid delivery lumen 18 and imaging lumen 20.

As seen in the example of FIGS. 2A and 2B, deployment catheter 16 may be manipulated to position deployed imaging hood 12 against or near the underlying tissue region of interest to be imaged, in this example a portion of annulus A of mitral valve MV within the left atrial chamber. As the surrounding blood 30 flows around imaging hood 12 and within open area 26 defined within imaging hood 12, as seen in FIG. 2A, the underlying annulus A is obstructed by the opaque blood 30 and is difficult to view through the imaging lumen 20. The translucent fluid 28, such as saline, may then be pumped through fluid delivery lumen 18, intermittently or continuously, until the blood 30 is at least partially, and preferably completely, displaced from within open area 26 by fluid 28, as shown in FIG. 2B.

Although contact edge 22 need not directly contact the underlying tissue, it is at least preferably brought into close proximity to the tissue such that the flow of clear fluid 28 from open area 26 may be maintained to inhibit significant backflow of blood 30 back into open area 26. Contact edge 22 may also be made of a soft elastomeric material such as certain soft grades of silicone or polyurethane, as typically known, to help contact edge 22 conform to an uneven or rough underlying anatomical tissue surface. Once the blood 30 has been displaced from imaging hood 12, an image may then be viewed of the underlying tissue through the clear fluid 30. This image may then be recorded or available for real-time viewing for performing a therapeutic procedure. The positive flow of fluid 28 may be maintained continuously to provide for clear viewing of the underlying tissue. Alternatively, the fluid 28 may be pumped temporarily or sporadically only until a clear view of the tissue is available to be imaged and recorded, at which point the fluid flow 28 may cease and blood 30 may be allowed to seep or flow back into imaging hood 12. This process may be repeated a number of times at the same tissue region or at multiple tissue regions.

FIG. 3A shows a partial cross-sectional view of an example where one or more optical fiber bundles 32 may be positioned within the catheter and within imaging hood 12 to provide direct in-line imaging of the open area within hood 12. FIG. 3B shows another example where an imaging element 34 (e.g., CCD or CMOS electronic imager) may be placed along an interior surface of imaging hood 12 to provide imaging of the open area such that the imaging element 34 is off-axis relative to a longitudinal axis of the hood 12, as described in further detail below. The off-axis position of element 34 may provide for direct visualization and uninhibited access by instruments from the catheter to the underlying tissue during treatment.

In utilizing the imaging hood 12 in any one of the procedures described herein, the hood 12 may have an open field which is uncovered and clear to provide direct tissue contact between the hood interior and the underlying tissue to effect any number of treatments upon the tissue, as described above. Yet in additional variations, imaging hood 12 may utilize other configurations. An additional variation of the imaging hood 12 is shown in the perspective and end views, respectively, of FIGS. 4A and 4B, where imaging hood 12 includes at least one layer of a transparent elastomeric membrane 40 over the distal opening of hood 12. An aperture 42 having a diameter which is less than a diameter of the outer lip of imaging hood 12 may be defined over the center of membrane 40 where a longitudinal axis of the hood intersects the membrane such that the interior of hood 12 remains open and in fluid communication with the environment external to hood 12. Furthermore, aperture 42 may be sized, e.g., between 1 to 2 mm or more in diameter and membrane 40 can be made from any number of transparent elastomers such as silicone, polyurethane, latex, etc. such that contacted tissue may also be visualized through membrane 40 as well as through aperture 42.

Aperture 42 may function generally as a restricting passageway to reduce the rate of fluid out-flow from the hood 12 when the interior of the hood 12 is infused with the clear fluid through which underlying tissue regions may be visualized. Aside from restricting out-flow of clear fluid from within hood 12, aperture 42 may also restrict external surrounding fluids from entering hood 12 too rapidly. The reduction in the rate of fluid out-flow from the hood and blood in-flow into the hood may improve visualization conditions as hood 12 may be more readily filled with transparent fluid rather than being filled by opaque blood which may obstruct direct visualization by the visualization instruments.

Moreover, aperture 42 may be aligned with catheter 16 such that any instruments (e.g., piercing instruments, guidewires, tissue engagers, etc.) that are advanced into the hood interior may directly access the underlying tissue uninhibited or unrestricted for treatment through aperture 42. In other variations wherein aperture 42 may not be aligned with catheter 16, instruments passed through catheter 16 may still access the underlying tissue by simply piercing through membrane 40.

In an additional variation, FIGS. 5A and 5B show perspective and end views, respectively, of imaging hood 12 which includes membrane 40 with aperture 42 defined therethrough, as described above. This variation includes a plurality of additional openings 44 defined over membrane 40 surrounding aperture 42. Additional openings 44 may be uniformly sized, e.g., each less than 1 mm in diameter, to allow for the out-flow of the translucent fluid therethrough when in contact against the tissue surface. Moreover, although openings 44 are illustrated as uniform in size, the openings may be varied in size and their placement may also be non-uniform or random over membrane 40 rather than uniformly positioned about aperture 42 in FIG. 5B. Furthermore, there are eight openings 44 shown in the figures although fewer than eight or more than eight openings 44 may also be utilized over membrane 40.

Additional details of tissue imaging and manipulation systems and methods which may be utilized with apparatus and methods described herein are further described, for example, in U.S. patent application Ser. No. 11/259,498 filed Oct. 25, 2005 (U.S. Pat. Pub. No. 2006/0184048 A1, which is incorporated herein by reference in its entirety.

As the assembly allows for ablation of tissue directly visualized through hood 12, FIG. 6 illustrates an example of a system configured for visualization and stent delivery. As shown in visualization assembly 50, hood 12 and deployment catheter 16 are coupled to handle 52. Fluid reservoir 54, shown in this example as a saline-filled bag reservoir, may be attached through handle 52 to provide the clearing fluid and/or ablation medium. An optical imaging assembly 56 coupled to an imaging element 34 positioned within or adjacent to hood 12 may extend proximally through handle 52 and be coupled to imaging processor assembly 58 for processing the images detected within hood 12. The video processor assembly 58 may process the detected images within hood 12 for display upon video display 60. Handle 52 may further incorporate a delivery channel or port 62 through which a stent delivery assembly may be introduced for deployment of one or more stents into the patient's body through the deployment catheter 16 and hood 12.

One example for deploying a stent while under direct visualization is shown in the partial cross-sectional views of FIGS. 7A to 7C. Introducer sheath 14 may be introduced into the patient's body utilizing conventional approaches such that the sheath 14 is advanced intravascularly through the descending aorta DA and aortic arch AC and into the ascending aorta AA, where a guidewire 70 may be advanced through sheath 14 and into, e.g., the right coronary artery RCA. Treatment may be affected not only within and around the right coronary artery RCA, but also the left coronary artery LCA, left anterior descending artery, left circumflex artery, or any other vessel accessible by the assembly. As the guidewire 70 is positioned within, e.g., the lumen 72 of RCA as shown in FIG. 7A, deployment catheter 16 and hood 12 may be deployed from sheath 14 and advanced along guidewire 70, as shown in FIG. 7B, until the circumference of hood 12 contacts against or in proximity to ostium OS. Guidewire 70 may be omitted from the procedure, if so desired.

Once hood 12 is in contact against the ostium OS, the clearing fluid may be introduced within the open area of hood 12 to purge the blood from the hood interior to provide a clear field through which an imaging element positioned within or along hood 12 may visualize through to view the underlying tissue surrounding the ostium OS and at least a portion of the vessel wall extending into lumen 72.

As illustrated in the detail partial cross-sectional views of FIGS. 8A to 8C, with hood 12 positioned against or in proximity to ostium OS and the visual field cleared to provide visual imaging by imager 34, a stent delivery assembly 80 having an inflatable balloon 82 in an un-inflated low-profile configuration and a stent 84 crimped or otherwise positioned upon balloon 82 may be advanced through catheter 16 and distally out from hood 12 until stent assembly 80 is positioned in proximity or adjacent to, e.g., an ostial lesion 86, which is to be treated, as shown in FIG. 8A. Imager 34 may be used to directly visualize at least partially into lumen 72 as the purged clearing fluid exits hood 12 and down through lumen 72 to provide an image of the lesion 86 to be treated.

With stent assembly 80 desirably positioned and confirmed by direct visualization, balloon 82 may be inflated to expand stent 84 over lesion 86, as shown in FIG. 8B, also while under visualization. Balloon 82 may be subsequently deflated and then retracted back into hood 12 and catheter 16 leaving the deployed stent 84 positioned desirably within lumen 72. Imager 34 may be used to visually confirm the deployment and positioning of stent 84 within lumen 72, as shown in FIG. 8C.

In determining the size of the ostial lesion to be treated, the imaging capabilities of the hood 12 may be utilized for optimally treating the patient by directly measuring not only the lesion but also the diameter of the vessel lumen for determining an appropriate stent to be deployed as the diameter of the vessel as well as the axial length of the lesion may affect the shape and size of the stent.

One example is illustrated in the partial cross-sectional area of FIG. 9A, which shows hood 12 positioned against ostium OS with imager 34 visualizing the encompassed tissue and lesion 86. A measurement catheter 90 having a number of gradations 92 with known distances may be advanced through hood 12 and into lumen 72. With the purging fluid introduced through hood 12 and into lumen 72, the markings on catheter 90 may be viewed and compared to the lesion 86 directly to provide a more accurate measurement of the lesion length than provided by a fluoroscopic image alone.

FIG. 9B shows another example where one or more measurement baskets or expandable members 92, 94, 96, 98 (e.g., wire or mesh baskets, distensible membranes, etc.) may be utilized to measure an inner diameter of the vessel. Expandable baskets or members each having a known expanded diameter may be positioned along a support catheter 100 and advanced distally from hood 12 and into lumen 72 to measure a diameter of the vessel interior. The one or more members may be positioned along catheter 100 in increasing order of diameter size with colors, designs, markings, or other visual indications used to identify each particular member. Although four members 92, 94, 96, 98 are shown in the example, as few as one member or greater than four members may be utilized. Moreover, each subsequent member may be stepped in diameter size by a predetermined amount as desired. The members may be passed through the vessel ostium while under visualization in increasing order of diameter until the expanded basket is compressed or unable to cannulate the ostium OS. The inner diameter of the vessel can thus be calculated by considering the diameter of the member which is blocked from entering ostium OS. With the calculated length and diameter of the vessel and lesion to be treated, an appropriate stent 84 may be selected for placement at the ostial lesion 86.

In use, catheter 100 may be advanced through hood 12 with the one or more measurement baskets or expandable members 92, 94, 96, 98 configured in a delivery profile while constrained within sheath 102, as shown in the detail side view of FIG. 10A. Sheath 102 may be retracted, as indicated by the arrows, or catheter 100 may be advanced distally until each respective member is deployed and expanded, as shown in FIG. 10B, until all the members 92, 94, 96, 98 or an appropriate number of members have been deployed and expanded within the vessel lumen and/or proximate to the ostium OS, as shown in FIG. 10C.

In another variation, FIGS. 11A to 11E show cross-sectional views of a deployment catheter 16 utilizing an inflatable visualization balloon assembly 110 which remains enclosed rather than an open hood 12. The stent assembly 80 may be utilized with the visualization balloon 110 and positioned either through a lumen defined through the visualization balloon 110 or distally upon balloon 82, which in this example may be coupled as a separate balloon or integrated with visualization balloon 110 as a single balloon assembly, as shown in FIG. 1 IA. Balloon 82 in this variation may comprise a thin, tube-like deployment balloon with stent 84 crimped around it and with the relatively larger transparent visualization balloon 110 positioned proximally. Imager 34 may be positioned within balloon 110 for imaging through the balloons 110 and/or 82 for visualizing the ostium OS as well as the vessel walls.

With guidewire 70 advanced through the lumen 72 of, e.g., right coronary artery RCA, stent 84 and balloon 82 maybe inserted at least partially into the right coronary artery RCA. The proximal visualization balloon 110 may be inflated and pushed distally until the balloon surface is firmly in contact with the vessel ostium OS and free from blood between the balloon-tissue interface to visualize the ostium OS, as shown in FIG. 11B. The positioning of the stent 84 with respect to the ostial lesion 86 can thus be viewed with imaging element 34 inside the visualization balloon 110. Stent 84 can then be manipulated by pushing or pulling the balloon system against the ostial lesion 86. With the inflated visualization balloon 110 firmly pressing against the ostium OS, the operator may also be able to ensure that the stent 84 is not placed too proximally such that parts of the stent 84 is not protruding into the aortic lumen which can cause thrombus or other complications.

Upon visual confirmation that the stent 84 is positioned at its desired location and overlapping the ostial lesion 86, the deployment balloon 82 may be inflated until the stent 84 attains its stable configuration and is securely placed within the vessel, as shown in FIG. 11C, while the entire procedure is viewed under direct visualization with imaging element 34. Upon the successful placement of the stent 84 at the site of ostial lesion 86, one or both balloon 82 and/or visualization balloon 110 may be deflated and reduced to their original configuration and withdrawn, as shown in FIG. 11D. The assembly may then be withdrawn along with the guidewire 70 leaving behind the stent 84, as shown in FIG. 11E.

In yet another variation, FIG. 12A shows a side view of a deployment catheter 16 with hood 12 having an angled interface 120 which is angled relative to catheter 16. In this variation, an asymmetric, slanted hood 12 may be used to facilitate navigation within the aorta as the hood 12 may be better able to engage against a tissue region or ostium and establish visualization without the need to steer and/or articulate the catheter shaft perpendicularly within the narrow aorta lumen. As illustrated in FIG. 12B, angled interface 120 can be used to access the right coronary artery RCA without having to steer/articulate the deployment catheter 16 perpendicularly relative to ostium OS. A section of catheter 16 proximal to hood 12 can also optionally comprise a passive pre-shaped bend in place of an actively steerable section to assist the hood 12 in visualizing and accessing the coronary arteries.

The applications of the disclosed invention discussed above are not limited to certain treatments or regions of the body, but may include any number of other treatments and areas of the body. Modification of the above-described methods and devices for carrying out the invention, and variations of aspects of the invention that are obvious to those of skill in the arts are intended to be within the scope of this disclosure. Moreover, various combinations of aspects between examples are also contemplated and are considered to be within the scope of this disclosure as well. 

What is claimed is:
 1. A method of deploying a stent under direct visualization, comprising: intravascularly advancing a reconfigurable hood structure having a distal end in a low-profile configuration into proximity to a vessel opening; reconfiguring the hood structure into a deployed configuration which defines an open area bounded at least in part by the hood structure and by a membrane extending across the hood structure distal end, wherein the open area is in fluid communication with an environment external to the hood structure via an aperture in the membrane; positioning the open area over the vessel opening; purging blood from the open area by introducing a clearing fluid through the open area of the hood structure and into the environment; positioning a stent through the open area into proximity to a lesion along the vessel while visualizing the stent through the clearing fluid; and expanding the stent to contact the lesion along the vessel.
 2. The method of claim 1 further comprising visualizing the vessel within the open area through the clearing fluid.
 3. The method of claim 1 wherein positioning a stent comprises advancing the stent upon an inflatable balloon member.
 4. The method of claim 3 wherein expanding the stent comprises inflating the balloon member into contact against the lesion.
 5. The method of claim 1 further comprising measuring a length of the lesion prior to positioning a stent through the open area.
 6. The method of claim 1 further comprising measuring a diameter of the vessel prior to positioning a stent through the open area.
 7. The method of claim 1 further comprising visually inspecting the stent expanded against the lesion.
 8. The method of claim 1 wherein positioning the open area over the vessel opening includes positioning the open area over a vessel opening to a vessel lumen such that the hood contacts tissue adjacent to the vessel opening and external to the vessel lumen.
 9. The method of claim 8 further comprising visualizing the vessel lumen and the tissue adjacent to the vessel opening through the open area. 